Vibratory feeding and vibratory conveying apparatus systems have been in use for many years. While initially such systems were primarily fixed rate, i.e., the vibrations were of a fixed amplitude or at a fixed frequency, more recently systems have been devised to vary the amplitude or frequency of the vibratory movement of such devices. Where the vibration generating system includes an electric motor, the development of a squirrel cage motor has provided a variable speed motor capable of varying the frequency of the vibratory movement. As the frequency approaches or departs from the natural frequency of the system, the amplitude of the vibrational movement imparted is varied In addition, other systems may vary the vibratory force imparted to the vibrating apparatus, for example, the system shown in my U.S. Pat. No. 3,358,815.
The foregoing systems, however, provided primarily for manual adjustment of the amplitude or frequency, usually by visual operation of the feed or conveying speed and manual adjustment to achieve a desired result, or they may be at least partially automatic as shown in my U.S. Pat. No. 4,168,774.